ASCII is the abbreviation for American Standard Code for Information Interchange. It is a system of representing characters using 8-bits. The 8th bit is actually a parity bit used for parity check which is a form of error-checking. Since the parity check uses up one bit, only 7 bits are available for characters representation. Therefore, ASCII typically represents only 128 characters (calculated from 2 ^ 7 = 128). For example the ASCII code for the lower case letter b is 98 and that of upper case letter A is 65.
